Peroxides have been used since long for laundry washing, for bleaching processes in textile and paper industry and also as antimicrobial agents. Peroxidase enzymes are used in these applications to convert hydrogen peroxide into radicals. Certain organic compounds such as p-hydroxycinnamic acid, 2,4-dichlorophenol, p-hydroxybenzene sulphonate, vanillin, p-hydroxybenzoic acid and derivatives have been described in industrial processes for textile bleaching (WO9218683).
The antimicrobial activity of peroxidase based systems depends on the type of electron donor being used. EP514417 demonstrates the effect of iodide and thiocyanate ions on the antimicrobial activity versus bacteria and fungi. This patent also shows an enhancing effect of anti-oxidants on the peroxidase activity. The compositions described to be active against both bacteria and yeast are described to comprise between 0.5 to 200 mg/kg iodide anions, between 2 to 100 mg/kg thiocyanate anions, and between 0.2 to 100 g/kg D-glucose. The weight:weight ratio of iodide:thiocyanate anions in the described compositions is between 0.1:1 to 50:1 and the combined anion weight concentration is at least 5 mg/kg. These compositions further comprise between 10 to 100000 U/kg lactoperoxidase, and contain between 150 to 4000 U/kg glucose oxidase. U.S. Pat. No. 4,476,108 discloses a method for producing bactericidal free radicals in the mouth over a controlled time period by applying a combination of a peroxidase, a peroxide and a source of donor molecules within predetermined concentration levels. The preparation is preferably used in a carrier liquid or paste. The carrier can be water, toothpaste of standard formulation, mouthwash of standard formulation, chewing gum, prophylaxis paste, denture cleaner and oral cleansing gels. More particularly, it discloses anti-microbial compositions for oral application with a short-term activity (less than two minutes) using peroxide, a peroxidase, a donor molecule such as phenylethylamine, tyrosine, tryptophan, benzoic acid, salicylic acid, hydroquinone, dehydrophenylalanine, vanillin and para-aminobenzoic acid. US20020119136 describes a class of dialkoxyphenol compounds (e.g. acetosyringone and alkylsyringates) with an enhancing effect on peroxidases.
Antimicrobial activity as such against fungi and bacteria has been attributed to aromatic flavouring compounds such as syringaldehyde and vanillin [Fitzgerald et al. (2005). J Agric Food Chem. 53, 1769-1775; Fitzgerald et al. (2004). J Appl Microbiol. 97, 104-113]. The antimicrobial activity is however only observed at high concentrations and after prolonged periods of incubation. Despite the existing variety of peroxidase enhancing compounds there is a need for additional peroxidase enhancing compounds, which are non-toxic, are sufficiently soluble for use in aqueous compositions and have a desired prolonged antimicrobial effect for medical applications such as disinfecting wounds.